I usually get more nervous when I think I am winning in a sharp position; it is like I am nervous to continue holding the initiative. A scenario like me playing a (hopefully sound) sacrifice makes me more nervous, because I know I can easily blow the game if I lose the initiative or miss a small detail.
Whenever I am in a "losing" position, I usually try to calm down. Take some deep breaths and try looking at the position in a creative way. If losing, then how can I gain the advantage? Can I create counterplay? Maybe I can complicate the position? Perhaps it is psychological, but I don't get as anxious in losing positions; I don't have as much to lose, so I fight with everything I've got. The positions that scare me the most are the ones that I believe are theoretically winning for me, but tough to convert, or navigate.
I usually struck with panic attack whenever i have bad position. The symptoms are so strong that i often lost the desire to do defence. Countless hours of practising tactics on defense is not helping me. I give up whenever i have bad position not by resigning but by playing more nonsensical move and it always results in deteriorating my position even further more from where i have no hope to continue the struggle . This cycle usually goes on and on. I mean: bad position, bad move, created more bad position, again bad move and created even more bad position.